In recent years, electric vehicles and hybrid vehicles are beginning to prevail, which include devices such as motors and batteries, and travel by driving the motors with power stored in the batteries. The electric vehicles charge their batteries with power supplied from external power supply devices. As for the hybrid vehicles, plug-in hybrid vehicles have been practically used, which allow their batteries to be charged by external power supply devices. The external power supply devices are power supply devices installed in ordinary houses or facilities such as commercial charging stations. When a power supply device supplies power to a vehicle, a plug at an end of a charging cable connected to the power supply device is connected to a power supply port which is provided in the vehicle as a power receiving connector. Then, power is supplied from the power supply device to the vehicle via a power supply line contained in the charging cable, and thereby the battery is charged.
Not only the power supply line but also other lines such as a grounding line, a control line, and the like are contained in the charging cable. The control line is a line used for transmission of a control signal such as a control pilot signal or the like used for control of power supply to the power storage device. By transmitting and receiving the control signal between the power supply device and the vehicle via the control line, various states are detected such as the connection state of the charging cable, whether charging is possible or not, the state of charging, and the like, and charging control is performed according to the detected states.
Further, for practical use of vehicles that need external power supply, such as electric vehicles and hybrid vehicles, a communication function is required, which allows a vehicle and a power supply device to transmit and receive information for power supply control, and communication information for management of the amount of power, accounting, or the like.
Thus, standardization of communication such as inband communication has been progressed, in which a communication signal is superposed on a control signal to be transmitted and received between a vehicle and a power supply device (refer to Non-Patent Literature 1, for example).
FIG. 9 is an illustrative diagram showing an exemplary configuration of a system standardization of which is in progress. In FIG. 9, reference numeral 1000 denotes a vehicle. When the vehicle 1000 is supplied with power from a power supply device 2000, the vehicle 1000 is connected to the power supply device 2000 via a charging cable 3000. The charging cable 3000 contains a pair of power supply lines 3001 and 3002 used for power supply, a grounding line 3003 which is a conducting wire for grounding, and a control line 3004 for transmitting a control signal such as a control pilot signal (CPLT) used for charging control.
An end of the charging cable 3000 is connected to the power supply device 2000 side, and a plug 3005 is provided on the other end of the charging cable 3000. The plug 3005 is connected to a power receiving connector 1001 provided as a connection part at a power supply port on the vehicle 1000 side, and thereby power supply is enabled.
The power supply device 2000 includes a power supply section 2001 that supplies AC power, a charging control section 2002 that performs communication relating to charging control, a communication section 2003 that transmits and receives a communication signal, and a superposition/separation section 2004 that performs superposition and separation of the communication signal on and from the grounding line 3003 and the control line 3004.
The superposition/separation section 2004 superposes various communication signals on the grounding line 3003 and the control line 3004, and separates superposed various communication signals. When the superposition/separation section 2004 superposes various communication signals output from the communication section 2003, and inputs separated various communication signals to the communication section 2003, the communication section 2003 is allowed to perform communication.
The vehicle 1000 includes the power receiving connector 1001, a battery 1002, a charging device 1003 that charges the battery 1002, a charging control device 1004 that performs communication relating to charging control, a communication device 1005 that transmits and receives communication signals, and a superposition/separation unit 1006 that performs superposition and separation of the communication signals on and from the grounding line 3003 and the control line 3004.
The superposition/separation unit 1006 superposes various communication signals on the grounding line 3003 and the control line 3004, and separates superposed various communication signals. When the superposition/separation unit 1006 superposes various communication signals output from the communication device 1005, and inputs separated various communication signals to the communication device 1005, the communication device 1005 is allowed to perform communication.
However, in the system relating to communication such as inband communication as shown in FIG. 9, if a communication signal transmitted through the control line 3004 crosstalks the power supply lines 3001 and 3002, noise may occur in the power supply lines 3001 and 3002.
An upper limit of voltage of noise caused in the power supply lines 3001 and 3002 due to crosstalk of a communication signal is defined as the CISPR 22 standard by the International Special Committee on Radio Interference. Control such as output suppression for the communication signal is performed so that the voltage value of noise does not exceed the upper limit value defined in the standard over the entire frequency relating to the communication.